A lot of the small engines that you buy today are not adjustable, adjusting the carburetor is impossible for some carbs. They come pre-set from the factory. For the Mantis cultivator/tiller, also cleaning out the fuel system will help you.
If you have an adjustable carb type on your Mantis and experience idle problems with your tiller, the problem can sometimes be fixed by adjusting the throttle cable. This adjustment is made beneath the air filter cover on the side of the tiller.
If your Mantis has carburetor screws, then you should have the main mixture screw you tuned by running the engine at full throttle. Further adjusting it up and down until the engine barely 4-strokes under full throttle, under no load.
The idle mixture screw you adjust by letting the engine drop from the full throttle and making sure the engine does not stall
The idle speed screw you adjust so that the engine is just about vibrates the tines at idle.
What to Do if Your Engine Idles Too High
What if your engine runs too fast … or if the tines turn the instant you start the Tiller? You may need to adjust the idle screw by itself right below the H and L screws. Gently turn it counter- clockwise. You’ll know you’ve adjusted it correctly when the axles do not turn at low idle.
If you continue to have idle problems, you may need to adjust the throttle cable.
First, locate the metal triangle at the end of the throttle cable (picture 1).
The idle screw must touch this triangle. But, if the throttle cable’s too tight, you’ll see a gap between the idle screw and the triangle.
To fix this, loosen the top nut that holds the throttle cable in place. (Picture 2) (Use a 10mm holds the throttle cable. Locate the metal “button” on the triangle. This is the swivel. The large end of the throttle cable must be inside the slot in this swivel. (Picture 3)
What to Do if Your Engine Runs “Rough”
If your engine runs “rough” or stalls, you may need to adjust the carburetor and idle screws.
If you remove the air cleaner cover, you’ll see the two carburetor, adjustment screws next to the black choke button.
The “RED” screw is the HIGH-speed adjustment…The “WHITE” screw is the low-speed adjustment.
First, remove the tines from the axle. Then start the engine. Let it run for two to three minutes.
Now, turn the RED, high- speed screw counter-clockwise all the way to stop…Then turn the WHITE, low-speed screw halfway between the counterclockwise and clockwise stop positions.
Now restart the engine to finish the carburetor adjustment.
Run the engine at full speed two or three seconds to clear out any excess fuel. Then return to idle.
Now, accelerate the engine to full throttle several times to check for a smooth transition from idle to high speed.
If the engine hesitates then turn the WHITE, low-speed screw counter-clockwise one-eighth of a turn. Then accelerate the engine.
Repeat the adjustment until you get a smooth transition to high speed